Harmonic generator



Aug. 23, 1949.

N. B. BLAKE 2,479,551

HARMONIC GENERATOR Filed Sept. 12, 14e

65 404.6 V 48 J4 I m I 1. fig? +22 T T T 51 T+ T- a 46 l &2 6

3 a 2 v INVENTOR. C Norman B BlaKe d l-vcy A T i OFENEYS Patented Aug. 23, 1949 HARMONIC GENERATOR Norman B. Blake, Beaumont, Tex., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Application September 12, 1946, Serial No. 696,587

'7 Claims.

This invention relates to a harmonic generator designed to secure a maximum output of upper harmonics of a fundamental frequency.

It sometimes happens that it is desired to secure a series of harmonics of some fundamental frequency for the purpose, for example, of establishing harmonic bands for simultaneous or interrelated uses. As an example, there may be cited multiple recording of signals on a single magnetic tape or Wire. As an example illustrative of this, reference may be made to the application of Alfred C. Winterhalter, Serial Number 656,803, filed March 25, 1946, in which the harmonic generator of the present invention is employed for the purpose of securing a series of harmonically relatedbands modulated by separate signals and adapted to be simultaneously recorded. In general, the requirements of such a harmonic generator involve the transformation of a sinusoidal fundamental frequency wave into a wave having a rectangular or similar shape with sharp breaks in its outline of such nature that a Fourier analysis will show a high content of harmonics. In accordance with the present invention substantial outputs of harmonics ranging up to the fifteenth or higher may be secured.

The object of the present invention is the provision of means for securing harmonic outputs of the type just indicated. This object, together with other objects relating to details will become apparent from the following description read in conjunction with the accompanying drawing in which:

Figure 1 illustrates in diagram a preferred circuit embodying the invention; and

Figure 2 shows wave forms of the voltages at various points in the circuit.

Essentially, the circuit involves an oscillator delivering a sinusoidal output to a circuit giving rise to the harmonics of the oscillator frequency.

The oscillator 2 may comprise a tuning fork 40 having a frequency, for example, of 500 cycles, together with its driving system. The driving coil indicated at 42 is energized by the driving system which includes the pick-up 44, the amplifier tube 46 and its connections and the amplifier tube or tubes 48 illustrated as a twin triode, one section of which through the line 50 energizes the driving coil 42 and the other section of which through the line 52 feeds the output trans-former 54, the output being delivered through the lines 56 and 51. The system here involved is essentially conventional for the driving of a tuning fork and need not be described in further detail,

2 the functions of the circuit being well understood by those skilled in the art.

The lines 56 and 57' feed the harmonic generator which is of novel construction, the induced voltage in the secondary of the transformer 5 being a substantially pure sine wave. The line 56 is connected to the anode E0 of a gas-filled rectifier tube 53, such as an 024 (with its anodes connected together), the cathode 62 of which is connected through a battery 54 to the line 51. Beyond the connection to the anode (ill, the line 56 includes a resistor 66 and is beyond this resistor connected to the cathode l0 of a diode 68, the anode E2 of which is connected through a battery 14 to the line 51. A twin diode, such as indicated, for example a 7A6, may be used with its cathodes and anodes connected together, as illustrated, to form, in eiiect, a single diode. The output is fed through a condenser it, across a resistor 18 so that the harmonics which are generated are delivered through lines connected to the ends ofthe resistor. The battery 54 may have a voltage of 90 volts, and battery 14 a voltage of 22 volts for the particular tubes indicated.

The operation of the harmonic generator may be described as follows. As the input wave rises positively from a zero value in the'line 56, no current will flow through the tube 53 until the anode-cathode voltage in that tube rises to the firing value which in the instance indicated may be about 300 volts. Prior to firing, therefore, the line 56 will rise to a voltage of, say, 210 volts with reference to line 51'. Since the cathode iii of the tube 58 is then positive, it cannot conduct. After firing, the anode-cathode drop in tube 58 becomes approximately 24 volts, and a heavy surge of current occurs through the tube.

The line will accordingly become negative with respect to the line 5'5 by an amount equal to the difference between the voltage of the battery E4 and the voltage drop through the tube 58, i. e., in the example given, by 55 volts. Tube 58 will then remain conductive through the remainder of the positive half cycle and during the beginning of the negative half cycle until the applied voltage reached a negative value of 66 volts whereupon the tube 58 will. be extinguished and the line 55 will thereafter have, relative to the line 51, a negative potential corresponding to the remaining half cycle of the voltage induced in the secondary of the transformer 54.

If the output were taken directly from the lines 56 and 57, the negative swing thus involved would introduce a considerable fundamental component into the output adding to the problem of filtering. Furthermore, this negative swing would reduce the amplitude of some of the higher harmonies. The function of the combination of the diode 68 and resistor 66 is to remove by limiting action the negative voltage swings. This action may be explained as follows:

When the anode 6!] becomes negative by the amount of 56 volts with respect to line 51, the battery 14 would, if the diode were non-conducting, cause the anode E2 of the diode to become positive with respect to its cathode by 66 volts plus the potential of battery 14, i. e., 88 volts in the example given. Actually the diode is conductive, and the voltage drops through the resistance 66 and the diode will cause the potentialat the right of resistance to become slightly positive with respect to the line This condition .continues until the tube 58 is extinguished. Thereupon the line 56 becomes more negative as the negative half cycle approaches its peak and cathode 19 may become slightly negative withrespect to line 51'. Following the peak of the negative half cycle, the potential of the cathode rises until early in the next positive half cycle when out off occurs and the diode becomes non-conducting. Both tubes will then be non-conducting and consequently the potential at the right of resistance $5 with respect to line 5? follows the positive half cycle of voltage induced in the transformer secondary until the voltage is sufficiently high for the tube 58 to fire.

The foregoing will become apparent from an examination of Figure 2 in which Wave form A is the substantially pure sine wave induced in transformer 54. Oscillogram B shows the volt-- age wave form across lines 5-5 and 5? wherein In is the since wave voltage curve existing up to a value of 210 volts. At this value, tube 56 becomes conductive and the voltage across conductors 5S and ill drops to a negative 66 volts as shown in b2. This voltage continues until the impressed sine wave becomes more negative than 66 volts whereupon tube 58 is extinguished and the voltage wave proceeds through the remainder of the normal negative half cycle as shown in D3. Oscillogram C shows the output voltage of the harmonic generator wherein the voltage rise 01 reaches a peak somewhat lower than 210 volts due to the voltage drop across resistor 65. The voltage drop is arrested at a low positive value 02 when the diode 68 becomes conductive. This condition continues until tube 58 is extinguished and thereupon the voltage becomes more negative at 03 until slightly before the end of the negative half cycle.

As a result of the foregoing, the output voltage consists of sharp peaks of substantially sinusoidal rises .followed by steep drops with low and negligible values between these peaks. The wave thus produced has a high harmonic content containing large amplitudes of even such high harmonies as the fifteenth.

It will be evident that various changes may be made in details without departing from the scope of the invention as defined in the following claims.

What I claim and desire to protect by Letters Patent is:

l. A harmonic generator comprising a pair of input lines, a gas-filled tube having its anode connected to one of said lines and its cathode connected to the other of said lines through a source of direct potential having its negative terminal connected to said cathode, a thermionic rectifier with its cathode connected to the first line and its anode connected to the second line through a source of direct potential having its positive terminal connected to the last mentioned anode, and means for supplying alternating current to said lines.

2. A harmonic generator comprising a pair of input lines, a gas-filled tube having its anode connected to one of said lines and its cathode connected to the other of said lines through a source of direct potential having its negative terminal connected to said cathode, a rectifier connected to the first line and through a source of direct potential to the second line, the rectifier being conductive when its terminal connected to the first line is negative, and the last mentioned source of direct potential having its negative terminal connected to said second line, and means for supplying alternating current to said lines.

3. A harmonic generator comprising a pair or input lines, a gas-filled tube having its anode connected to one of said lines and its cathode connected to the other of said lines through a source of direct potential having its negative terminal connected to said cathode, a rectifier connected to the first line and through a source of direct potential to the second line, the rectifier being conductive when its terminal connected to the first line is negative, and the last mentioned source of direct potential havingits negative terminal connected to said second line, there being a resistance in the first line between the connections of the tubes thereto, and means for sup-' plying alternating current to said lines.

4. A harmonic generator comprising a pair of input lines, a gas-filled tube having its anode connected to one of said lines and its cathode connected to the other of said lines through a source of direct potential having its negative terminal connected to said cathode, a thermionic rectifier with its cathode connected to the first line and its anode connected to the second line through a source of direct potential having its positive terminal connected to the last mentioned anode, there being a resistance in the first line between the connections of the tubes thereto, and means 'for supplying alternating current to said lines.

5. A harmonic generator comprising a pair of input lines, a gas-filled rectifier tube having its anode connected to one of said lines and its cathode connected to the other of said lines through a source of direct potential having its negative terminal connected to said cathode, a rectifier tube with its cathode connected to the first line and its anode connected to the second line through a source of direct potential having its positive terminal connected to the last mentioned anode and means for supplying alternating current to said lines.

6. A harmonic generator comprising a pair of input lines, a series arrangement of a gas filled tube and a source of direct potential connected across said lines with said source connected to oppose the flow of current through the tube, a series arrangement of a rectifier and a source of direct potential connected across said lines with the last mentioned source connected to oppose the fiow of current through the rectifier, said tube and said rectifier being conductive in opposite directions between said lines, there being a resistance in one of said linesbetween its junctions to the two series arrangements, and means for supplying alternating current to said lines,

7. A harmonic generator comprising a pair of input lines, a series arrangement of a gas filled tube and a source of direct potential connected across said lines with. said source connected. to

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Morris June 2, 1942 Number 

